Light emitting device, method of manufacturing the same, light emitting device package and lighting system

ABSTRACT

A light emitting device includes an active layer formed between first and second semiconductor layers. The first semiconductor layer includes a first surface facing the active layer, a second surface opposing the first surface, and a side surface that includes a stepped portion. The stepped portion causes the side surface to extend beyond one of the first surface or second surface of the first semiconductor layer. A light emitting device may also be formed with a buffer layer that includes a stepped portion, and a light emitting device package and system may be formed from the light emitting devices.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. §119 of KoreanPatent Application No. 10-2010-0010204 filed on Feb. 4, 2010, which ishereby incorporated by reference in its entirety.

BACKGROUND

1. Field

One or more embodiments disclosed herein relate to the emission oflight.

2. Background

A light emitting diode (LED) is a semiconductor device that converts anelectrical signal into light. These devices typically have a stackstructure which includes a semiconductor layer of a first conductivitytype, an active layer, and a semiconductor layer of a secondconductivity type. Because of their size, LEDs have proven desirable formany applications. However, improvements are still needed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 4 are sectional diagrams showing a first embodiment of alight emitting device and a various stages of its manufacture.

FIGS. 5 to 7 are sectional diagrams showing a second embodiment of alight emitting device and various stages of its manufacture.

FIGS. 8 to 11 are sectional diagrams showing a third embodiment of alight emitting device and various stages of its manufacture.

FIGS. 12 to 15 are sectional diagrams showing a fourth embodiment of alight emitting device and various stages of its manufacture.

FIG. 16 is a diagram showing a mask layer and protrusions.

FIG. 17 is a diagram showing the same or another mask layer.

FIG. 18 is a diagram showing one embodiment of a light emitting devicepackage that may include any of the aforementioned embodiments of thelight emitting device.

FIG. 19 is a diagram showing one embodiment of a backlight unit that mayinclude any of the aforementioned embodiments of the light emittingdevice or package.

FIG. 20 is a diagram showing one embodiment of a lighting unit that mayinclude any of the aforementioned embodiments of the light emittingdevice or package.

DETAILED DESCRIPTION

FIGS. 1 to 4 show one embodiment of a light emitting device and variousstages of its manufacture. Referring first to FIG. 4, the light emittingdevice includes a light emitting structure layer 60 formed from asemiconductor layer 30 of a first conductivity type, an active layer 40and a semiconductor layer 50 of a second conductivity type, all of whichare supported by a growth substrate 10. The LED further includes a firstelectrode 70 formed on the first conductivity type semiconductor layer30, and a second electrode 80 formed on the second conductivity typesemiconductor layer 50.

A plurality of protrusions 11 are formed on the growth substrate 10. Theprotrusions 11 may be in a semi-spherical shape or another shape, and interms of materials may be formed, for example, from one or more of SiO₂,SiN, GaO, ZnO, or ITO. The protrusions 11 may serve to enhance the lightextraction efficiency of the light emitting device by allowing lightemitted from the active layer 40 to be scattered. The protrusions 11 mayprovided in various numbers and/or shapes in addition to those shown inFIG. 4.

As indicated, the semiconductor layers on the growth substrate 10include a first semiconductor layer, a second semiconductor layer, andthe active layer between the first semiconductor layer and the secondsemiconductor layer. In the current embodiment, the first semiconductorlayer is implemented by the first conductivity type semiconductor layer30 and the second semiconductor layer is implemented by the secondconductivity type semiconductor layer 50.

The first conductivity type semiconductor layer 30 is formed with astepped portion 31 at a lower edge surface thereof. The stepped portion31 may be formed by extending the lower edge surfaces of the firstconductivity type semiconductor layer 30. Some portions of the firstconductivity type semiconductor layer 30 are spaced apart from thegrowth substrate 10. Also, in one embodiment, at least a portion of thestepped portion 31 and the protrusions 11 may be disposed on the sameplane.

The first conductivity type semiconductor layer 30 includes a firstsurface contacting the active layer 40 and a second surface oppositelyfacing the first surface. The area of the second surface may be smallerthan a maximum area of the first conductivity type semiconductor layerdue to the stepped portion 31.

One embodiment of a method for manufacturing the light emitting deviceshown in FIG. 4 will now be discussed with reference to FIGS. 1 to 4.

Referring to FIG. 1, a growth substrate 10 is prepared and a pluralityof protrusions 11 and a mask layer 12 are formed on the growth substrate10. The growth substrate 10 may be formed, for example, of one or moreof sapphire (Al₂O₃), SiC, Si, GaAs, ZnO, MgO, GaN, Glass or Ga₂O₃. Themask layer 12 may be formed of the same material as that of theprotrusions 11, e.g., SiO₂, SiN, GaO, ZnO, or ITO.

FIG. 16 shows an example of a plane view of mask layer 12 andprotrusions 11. As shown in FIG. 16, the mask layer 12 may be formed sothat the growth substrate 10 is exposed so that the light emittingstructure layer 60 may be grown. That is, a plurality of light emittingstructure layer growth regions A may be defined by the mask layer 12.The light emitting structure layer 60 may not be grown on the mask layer12, and in such a case the light emitting structure layer 60 on thelight emitting structure layer growth regions A may be grown so thatthey are separated from each other by the mask layer 12. The protrusionsmay be partially formed on the light emitting structure layer growthregions A of the growth substrate 10 where the mask layer 12 is notformed.

FIG. 17 shows another view of mask layer 12. As shown, the mask layer 12formed on the growth substrate 10 and the light emitting structure layergrowth regions A are defined by mask layer 12. Also, the protrusions 11are not formed on the growth substrate 10, but a protrusion pattern 12 amay be formed on a side surface of the mask layer 12. This or anotherprotrusion pattern corresponding to protrusion pattern 12 a may beformed on a side surface of the first conductivity type semiconductorlayer 30 grown on the light emitting structure layer growth regions A.

Referring to FIG. 2, a light emitting structure layer 60, including thefirst conductivity type semiconductor layer 30, an active layer 40 and asecond conductivity type semiconductor layer 50, is grown on the growthsubstrate 10 on which the mask layer 12 and the protrusions 11 areformed.

The first conductivity type semiconductor layer 30 is grown on thegrowth substrate 10 to cover the protrusions 11 through a horizontalgrowth and a vertical growth and to partially cover the mask layer 12.

The mask layer 12 allows the light emitting structure layer 60 to begrown in multiple chip units on a substrate, for example, by dividingthe growth substrate 10 into a plurality of light emitting structurelayer growth regions A on which the light emitting structure 60 isgrown. Thus, instead of scribing the substrate into individual chipunits first (that is, right after formation of the light emittingstructure layer), the light emitting structure layer is grown intomultiple chip units on a single substrate.

More specifically, when the aforementioned scribing technique is used,the crystallinity of a cleavage surface may not be good. As a result,leakage current may flow into the cleavage surface. However, when thelight emitting structure layer is grown onto the substrate as separatedor divided chip units, the resulting light emitting structure layer 60is grown into a high quality thin layer having improved properties interms of crystallinity of the side surface.

The first conductivity type semiconductor layer 30 may be grown, forexample, as or into a GaN-based semiconductor layer including an n-typeimpurity such as silicon (Si), and the second conductivity typesemiconductor layer 50 may be grown as or into a GaN-based semiconductorlayer including a p-type impurity such as Mg.

The active layer 40 may be formed of InGaN layer/GaN layer having asingle quantum well structure or multi-quantum well structure bysupplying ammonia (NH₃), trimethylgallium (TMGa), and trimethylindium(TMIn).

Referring to FIG. 3, a mesa etching step for partially removing thesecond conductivity type semiconductor layer 50, the active layer 40 andthe first conductivity type semiconductor layer 30 is performed. By mesaetching, some of the first conductivity type semiconductor layer 30 isexposed in an upward direction. Thereafter, a first electrode 70 isformed on the first conductivity type semiconductor layer 30, and asecond electrode 80 is formed on the second conductivity typesemiconductor layer 50.

Referring to FIG. 4, the growth substrate 10 and the mask layer 12 arecut to divide the growth substrate 10 and the light emitting structurelayer 60 into chip units. The growth substrate 10 may be cut by ascribing method or breaking method, and the mask layer 12 may be removedby an etching method.

At this time, the mask layer 12 may be partially or completely removed.In the case where the mask layer 12 is removed completely as shown inFIG. 4, the stepped portion 31 is formed at a lower edge region of thefirst conductivity type semiconductor layer 30.

In the case where mask layer 12 is formed as shown in FIG. 17, aprotrusion pattern may be formed on a side surface of the firstconductivity type semiconductor layer.

FIGS. 5 to 7 show a second embodiment of a light emitting device andvarious stages of its manufacture. Referring first to FIG. 7, the secondembodiment of the light emitting device includes an undoped nitridelayer 20 is formed on a growth substrate 10 and a light emittingstructure layer 60 formed on the undoped nitride layer. The lightemitting structure layer includes a first conductivity typesemiconductor layer 30, an active layer 40, and a second conductivitytype semiconductor layer 50. In addition, the LED includes a firstelectrode 70 formed on the first conductivity type semiconductor layer30, and a second electrode 80 formed on the second conductivity typesemiconductor layer 50.

A plurality of protrusions 11 are formed on the growth substrate 10. Theprotrusions 11 may be in a semi-spherical shape or another shape, andmay be formed, for example, of one or more of SiO₂, SiN, GaO, ZnO, orITO. The protrusions 11 may serve to enhance the light extractionefficiency of the light emitting device by allowing light emitted fromthe active layer 40 to be scattered. The protrusions 11 may be providedin various numbers and/or shapes in addition to those shown.

As indicated, the semiconductor layers on the growth substrate 10include a first semiconductor layer, a second semiconductor layer, andthe active layer between the first semiconductor layer and the secondsemiconductor layer. In the current embodiment, the first semiconductorlayer includes the undoped nitride layer 20 and the first conductivitytype semiconductor layer 30, and the second semiconductor layer isincludes the second conductivity type semiconductor layer 50.

The undoped nitride layer 20 is formed with a stepped portion 21 at oneor more lower edge surfaces thereof. Some portions of the undopednitride layer 20 may be spaced apart from the growth substrate 10. Also,at least a portion of the stepped portion 21 and the protrusions 11 maybe disposed on the same plane.

The undoped nitride layer 20 may include a first surface contacting thefirst conductivity type semiconductor layer 30 and a second surfaceoppositely facing the first surface, and the area of the second surfacemay be smaller than a maximum area of the first conductivity typesemiconductor layer due to the stepped portion 21.

One method for manufacturing the second embodiment of the light emittingdevice will now be described with reference to FIGS. 5 to 7. Referringto FIG. 5, a growth substrate 10 is prepared and a plurality ofprotrusions 11 and a mask layer 12 are formed on the growth substrate10. The growth substrate 10 may be formed, for example, from one or moreof sapphire (Al₂O₃), SiC, Si, GaAs, ZnO, MgO, GaN, Glass or Ga₂O₃. Themask layer 12 may be formed of the same material as the protrusions 11and may be, for example, formed from one or more of SiO₂, SiN, GaO, ZnO,or ITO.

An undoped nitride layer 20 is grown on the growth substrate 10 on whichthe mask layer 12 and the protrusions 11 are formed. A light emittingstructure layer 60 including a first conductivity type semiconductorlayer 30, an active layer 40 and a second conductivity typesemiconductor layer 50 is grown on the undoped nitride layer 20.

The undoped nitride layer 20 is grown on the growth substrate 10 tocover the mask layer 12 and the protrusions 11 through a horizontalgrowth and a vertical growth. Although the undoped nitride layer 20 maynot intentionally doped with a first conductivity type impurity, theundoped nitride layer 20 is a nitride layer which may have the firstconductivity type conductivity, and may be, for example, formed ofUn-GaN layer.

The first conductivity type semiconductor layer 30 may be formed, forexample, of a GaN-based semiconductor layer including an n-type impuritysuch as silicon (Si), and the second conductivity type semiconductorlayer 50 may be formed of a GaN-based semiconductor layer including ap-type impurity such as Mg.

The active layer 40 may be formed of InGaN layer/GaN layer having asingle quantum well structure or multi-quantum well structure bysupplying ammonia (NH₃), trimethylgallium (TMGa), and trimethylindium(TMIn).

Referring to FIG. 6, the result of a mesa etching technique is shown forpartially removing the second conductivity type semiconductor layer 50,the active layer 40, and the first conductivity type semiconductor layer30. By mesa etching, some of the first conductivity type semiconductorlayer 30 is exposed in an upward direction.

Thereafter, a first electrode 70 is formed on the first conductivitytype semiconductor layer 30 and a second electrode 80 is formed on thesecond conductivity type semiconductor layer 50.

Referring to FIG. 7, the growth substrate 10 and the mask layer 12 arecut to divide the growth substrate 10 and the light emitting structurelayer 60 into chip units. The growth substrate 10 may be cut by ascribing method or a breaking method, and the mask layer 12 may beremoved by an etching method. At this time, the mask layer 12 may becompletely or partially removed. In the case where the mask layer 12 isremoved completely as shown in FIG. 7, the stepped portion 21 is formedat a lower edge region of the undoped nitride layer 20. Also, in thecase where the mask layer 12 is formed as shown in FIG. 17, a protrusionpattern may be formed on a side surface of the undoped nitride layerwhere the stepped portion 21 is formed.

FIGS. 8 to 11 show a third embodiment of a light emitting device andvarious stages of its manufacture. Referring first to FIG. 11, the lightemitting device includes a light emitting structure layer 60 formed froma first conductivity type semiconductor layer 30, an active layer 40,and a second conductivity type semiconductor layer 50. A first electrode70 is formed on the first conductivity type semiconductor layer 30 and asecond electrode 110 is formed under the second conductivity typesemiconductor layer 50.

The second electrode 110 includes an ohmic contact layer 111 under thesecond conductivity type semiconductor layer 50, a reflective layer 112under the ohmic contact layer 111, and a conductivity supportingsubstrate 113 under the reflective layer 112.

As indicated, the semiconductor layers on the second electrode 110include a first semiconductor layer, a second semiconductor layer, andthe active layer between the first semiconductor layer and the secondsemiconductor layer. In the current embodiment, the first semiconductorlayer is implemented by the first conductivity type semiconductor layer30, and the second semiconductor layer is implemented by the secondconductivity type semiconductor layer 50.

The first conductivity type semiconductor layer 30 is formed with astepped portion 31 at an upper side surface thereof and with uppergrooves 32 at an upper surface thereof. The upper grooves 32 may act asphotonic crystals which allow the light emitted from the active layer 40to be effectively extracted to an outside.

The first conductivity type semiconductor layer 30 includes a firstsurface contacting the active layer 40 and a second surface oppositelyfacing the first surface. The area of the second surface may be smallerthan a maximum area of the first conductivity type semiconductor layerdue to the stepped portion 31.

One method for manufacturing the third embodiment of the light emittingdevice is shown with reference to FIGS. 8 to 11. Referring to FIG. 8, agrowth substrate 10 is prepared and a plurality of protrusions 11 and amask layer 12 are formed on the growth substrate 10. The growthsubstrate 10 may be formed, for example, from one or more of sapphire(Al₂O₃), SiC, Si, GaAs, ZnO, MgO, GaN, Glass or Ga₂O₃, and mask layer 12may be formed of the same material as protrusions 11, e.g., one or moreof SiO₂, SiN, GaO, ZnO, or ITO.

A light emitting structure layer 60, including a first conductivity typesemiconductor layer 30, an active layer 40, and a second conductivitytype semiconductor layer 50, is grown on the growth substrate 10 onwhich the mask layer 12 and the protrusions 11 are formed. The firstconductivity type semiconductor layer 30 is grown on the growthsubstrate 10 to cover the mask layer 12 and the protrusions 11 through ahorizontal growth and a vertical growth.

The first conductivity type semiconductor layer 30 may be formed, forexample, from a GaN-based semiconductor layer including an n-typeimpurity such as silicon (Si), and the second conductivity typesemiconductor layer 50 may be formed, for example, from a GaN-basedsemiconductor layer including a p-type impurity such as Mg.

The active layer 40 may be formed of InGaN layer/GaN layer having asingle quantum well structure or multi-quantum well structure bysupplying ammonia (NH₃), trimethylgallium (TMGa), and trimethylindium(TMIn).

Referring to FIG. 9 since the light emitting structure layer 60 is growninto multiple chip unit on the substrate at ares defined by mask layer12, a spacing exists between the light emitting structure layers 60 thatare adjacent to each other. Therefore, a protective layer 90 is formedbetween the light emitting structure layer 60 and light emittingstructure layer 60. The protective layer 90 may be formed of a materialsuch as polyimide or SOG or another material.

A second electrode 110 is formed on the light emitting structure layer60 and the protective layer 90. The second electrode layer 110 may beformed by first forming an ohmic contact layer 111, forming a reflectivelayer 112 on the ohmic contact layer 111, and forming a conductivitysupporting substrate 113 on the reflective layer 112.

The conductivity supporting substrate 113 may be formed to include, forexample, at least one of copper (Cu), titanium (Ti), molybdenum (Mo),chromium (Cr), nickel (Ni), aluminum (Al), platinum (Pt), gold (Au),tungsten (W), or conductivity semiconductor material. The reflectivelayer 112 may be formed from a metal including, for example, at leastone of silver (Ag), aluminum (Al), copper (Cu), or nickel (Ni) having ahigh reflectivity. Also, the ohmic contact layer 111 may be formed of atransparent conductivity oxide, such as indium tin oxide (ITO),aluminum-doped zinc oxide (AZO), indium zinc oxide (IZO), antimony tinoxide (ATO), or zinc indium tin oxide (ZITO).

Referring to FIG. 10, the growth substrate 10, mask layer 12, protectivelayer 90, and protrusions 11 are removed. The growth substrate 10 may beremoved using, for example, a laser lift-off method or a chemicallift-off method. Since the mask layer 12 and the protrusions 11 aredisposed between the growth substrate 10 and the light emittingstructure layer 60, the growth substrate 10 can be easily separated fromthe light emitting structure layer 60. That is, because the mask layer12 and the protrusions 11 are not strongly bonded to the light emittingstructure layer 60, the more wide the area of the mask layer 12 and theprotrusions 11, the easier the separation of the growth substrate 10.

As the growth substrate 10 is separated, the protrusions 11 and the masklayer 12 can be easily separated, and the protective layer 90 can beremoved by using an etchant. As the protrusions 11 and the mask layer 12are removed, upper grooves 32 and stepped portions 31 are formed in thefirst conductivity type semiconductor layer 30. Referring to FIG. 11, afirst electrode 70 is formed on the first conductivity typesemiconductor layer 30 and then the second electrode 110 is separated.

FIGS. 12 to 15 show a fourth embodiment of a light emitting device andvarious stages of its manufacture. Referring to FIG. 15, the lightemitting device includes a light emitting structure layer 60 formed froma first conductivity type semiconductor layer 30, an active layer 40,and a second conductivity type semiconductor layer 50 is formed, and anundoped nitride layer 20 is formed on the first conductivity typesemiconductor layer 30.

A first electrode 70 is formed on the first conductivity typesemiconductor layer 30 exposed by selectively removing the undopednitride layer 20, and a second electrode 80 is formed under the secondconductivity type semiconductor layer 50.

As indicated, the semiconductor layers on the second electrode 110include a first semiconductor layer, a second semiconductor layer, andthe active layer between the first semiconductor layer and the secondsemiconductor layer. In the current embodiment, the first semiconductorlayer is implemented by the undoped nitride layer 20 and the firstconductivity type semiconductor layer 30, and the second semiconductorlayer is implemented by the second conductivity type semiconductor layer50.

The undoped nitride layer 20 is formed with a stepped portion 21 at anupper side surface thereof and with upper grooves 22 at an upper surfacethereof. The upper grooves 22 may act as photonic crystals, which allowthe light emitted from the active layer 40 to be effectively extractedto an outside. The undoped layer may be formed from a material otherthan an nitride, and the same is true of the undoped layer in the thirdand other embodiments described herein.

The undoped nitride layer 20 includes a first surface contacting thefirst conductivity type semiconductor layer 30 and a second surfaceoppositely facing the first surface. The area of the second surface maybe smaller than a maximum area of the first conductivity typesemiconductor layer due to the stepped portion 21.

One method for manufacturing the fourth embodiment of the light emittingdevice will now be described with reference to FIGS. 12 to 15. Referringto FIG. 12, a growth substrate 10 is prepared and a plurality ofprotrusions 11 and a mask layer 12 are formed on the growth substrate10. The growth substrate 10 may be formed, for example, from one or moreof sapphire (Al₂O₃), SiC, Si, GaAs, ZnO, MgO, GaN, Glass or Ga₂O₃. Themask layer 12 may be formed of the same material as that of theprotrusions 11 and may be, for example, formed of one or more of SiO₂,SiN, GaO, ZnO, or ITO.

The undoped nitride layer 20 is grown on the growth substrate 10 onwhich the mask layer 12 and the protrusions 11 are formed. A lightemitting structure layer 60, including a first conductivity typesemiconductor layer 30, an active layer 40, and a second conductivitytype semiconductor layer 50, is grown on the undoped nitride layer 20.The undoped nitride layer 20 is grown on the growth substrate 10 tocover the mask layer 12 and the protrusions 11 through a horizontalgrowth and a vertical growth.

The first conductivity type semiconductor layer 30 may be formed, forexample, from a GaN-based semiconductor layer including an n-typeimpurity such as silicon (Si), and the second conductivity typesemiconductor layer 50 may be formed, for example, from a GaN-basedsemiconductor layer including a p-type impurity such as Mg.

The active layer 40 may be formed of InGaN layer/GaN layer having asingle quantum well structure or multi-quantum well structure bysupplying ammonia (NH₃), trimethylgallium (TMGa), and trimethylindium(TMIn).

Referring to FIG. 13, because the light emitting structure layer 60 isgrown into chip units defined by the mask layer 12, a spacing existsbetween the light emitting structure layers 60 adjacent to each other.Therefore, a protective layer 90 may be formed between the lightemitting structure layer 60 and the light emitting structure layer 60.The protective layer 90 may be formed of a material such as polyimide orSOG or another material.

A second electrode 110 is formed on the light emitting structure layer60 and the protective layer 90. The second electrode layer 110 may beformed by first forming an ohmic contact layer 111, forming a reflectivelayer 112 on the ohmic contact layer 111, and forming a conductivitysupporting substrate 113 on the reflective layer 112.

The conductivity supporting substrate 113 may be formed to include atleast one of copper (Cu), titanium (Ti), molybdenum (Mo), chromium (Cr),nickel (Ni), aluminum (Al), platinum (Pt), gold (Au), tungsten (W), orconductivity semiconductor material. The reflective layer 112 may beformed to include a metal corresponding to at least one of silver (Ag),aluminum (Al), copper (Cu), or nickel (Ni) having a high reflectivity.Also, the ohmic contact layer 111 may be formed of a transparentconductivity oxide, such as indium tin oxide (ITO), aluminum-doped zincoxide (AZO), indium zinc oxide (IZO), antimony tin oxide (ATO), or zincindium tin oxide (ZITO).

Referring to FIG. 14, the growth substrate 10, mask layer 12, protectivelayer 90, and protrusions 11 are removed. The growth substrate 10 may beremoved using, for example, a laser lift-off method or a chemicallift-off method. Since the mask layer 12 and the protrusions 11 aredisposed between the growth substrate 10 and the undoped nitride layer20, the growth substrate 10 can be easily separated from the undopednitride layer 20. That is, since the mask layer 12 and the protrusions11 are not strongly bonded to the undoped nitride layer 20, the morewide the area of the mask layer 12 and the protrusions 11, the easierthe separation of the growth substrate 10.

As the growth substrate 10 is separated, the protrusions 11 and the masklayer 12 can be easily separated and the protective layer 90 can beremoved by using an etchant. Accordingly upper grooves 32 and steppedportions 31 are formed in the undoped nitride layer 20.

Referring to FIG. 15, the undoped nitride layer 20 is selectivelyremoved to expose the first conductivity type semiconductor layer 30,and a first electrode 70 is formed on the first conductivity typesemiconductor layer 30.

FIG. 18 shows a light emitting device package that includes any of theaforementioned embodiments of the light emitting device. Referring toFIG. 18, the light emitting device package 600 includes a package body300, first and second conductivity layers 310 and 320 mounted on thepackage body 300, a light emitting device 200 mounted on the packagebody 300 and electrically coupled to the first and second conductivitylayers 310 and 320, and a molding member 500 enclosing the lightemitting device 200.

The package body 300 may be formed to include, for example, one or moreof a silicon material, a synthetic resin material, or a metallicmaterial and may have an inclined surface around the light emittingdevice 200.

The first conductivity layer 310 and the second conductivity layer 320are electrically separated and supply electric power to the lightemitting device 200. Also, the first and second conductivity layers 310and 320 may reflect light generated from the light emitting device 200to increase light efficiency and may emit heat generated from the lightemitting device 200 to an outside or external location.

The light emitting device 200 may be any of the light emitting devicespreviously described, and light emitting device 200 may be mounted onthe package body 300 or on the first conductivity layer 310 or thesecond conductivity layer 320. The light emitting device 200 may beelectrically coupled to the first conductivity layer 310 and the secondconductivity layer 320 through a wire 400.

When the package of FIG. 18 is formed to include a light emitting device200 according to the first or second embodiments, two wires 400 areused. When the package is formed to include a light emitting device 200according to the third or fourth embodiments, only one wire 400 may beused. Alternatively, in the case where the light emitting device 200 isconnected by a flip chip method, the wire 400 may not be used at all.

The molding member 500 may be provided to enclose and protect the lightemitting device 100. A fluorescent material may be included in themolding member 500 to change the wavelength of light emitted from thelight emitting device 200. Because the light emitting device package 600employs a light emitting device 200 having enhanced light efficiency, itfollows that light emitting device package 600 will also demonstratesuperior light efficiency.

According to one embodiment, the light emitting device package 600 mayinclude a plurality of light emitting device packages arrayed onto asubstrate. A plurality of optical members, such as a light guide panel,a prism sheet, a diffusion sheet, a fluorescent sheet, and/or the like,may be arranged on a path of light emitted from the light emittingdevice package 600. The light emitting device package, substrate, andoptical members may function as a backlight unit or lighting unit, and alighting system may include, for example, a backlight unit, a lightingunit, an indicator unit, a lamp, a streetlamp, etc.

FIG. 19 shows a disassembled view of a backlight unit 1100 that includesa light emitting device or package according to any one of theaforementioned embodiment. The backlight unit 1100 may serve as alighting system for a variety of applications.

The backlight unit 1100 may include a bottom frame 1140, a light guidemember 1120 disposed in the bottom frame, and a light emitting module1110 disposed on at least one side surface of light guide member 1120and/or under light guide member 1120. A reflective sheet 1130 may bedisposed under the light guide member 1120.

The bottom frame 1140 may be formed in a box shape a top surface ofwhich is opened such that the light guide member 1120, the lightemitting module 1110 and the reflective sheet 1130 can be received. Thebottom frame 1140 may be formed of a metal or resin material, but othermaterials are also possible.

The light emitting module 1110 may include a substrate 700 and aplurality of light emitting device packages 600 mounted on the substrate700. The plurality of light emitting device packages 600 may providelight to the light guide member 1120. In the light emitting module 1110according to the current embodiment, it is illustratively shown that thelight emitting device packages 600 are mounted on substrate 700, but inother embodiments the light emitting devices may be mounted directly onthe substrate 700.

As shown in FIG. 19, the light emitting module 1110 may be disposed onat least one of inner side surfaces of the bottom frame 1140, and thusmay provide light to at least one of the side surfaces of the lightguide member 1120.

It is also to be understood that the light emitting module 1110 may bedisposed under the light guide member 1120 inside the bottom frame 1140to provide light toward a bottom surface of the light guide member 1120.However, the constitution may be modified according to the specificdesign requirements of the backlight unit 1100 according to, forexample, an intended application.

The light guide member 1120 may be disposed inside the bottom frame1140. The light guide member 1120 may convert the light provided fromthe light emitting module to a planar light source and guide theconverted plane light source to a display panel (not shown).

The light guide member 1120 may be, for example, a light guide panel(LGP). The LGP may be formed of, for example, one of acryl-series resinsuch as polymethyl metaacrylate (PMMA), polyethylene terephthlate (PET),poly carbonate (PC), COC, and polyethylene naphthalate resin.

An optical sheet 1150 may be disposed on the light guide member 1120,and may include, for example, at least one of a diffusion sheet, alight-condensing sheet, a brightness enhancement sheet and a fluorescentsheet. According to one example, the optical sheet 1150 may beconfigured by the diffusion sheet, the light-condensing sheet, thebrightness enhancement sheet and the fluorescent sheet stacked. In thiscase, the diffusion sheet 1150 diffuses the light emitted from the lightemitting module 1110 uniformly, and the diffused light may be condensedon the display panel (not shown) by the light-condensing sheet.

At this time, the light emitted from the light-condensing sheet is arandomly polarized light, and the brightness enhancement sheet mayincrease the polarization of the light emitted from the light-condensingsheet. The light-condensing sheet may be, for example, a horizontaland/or vertical prism sheet. Also, the brightness enhancement sheet maybe, for example, a dual brightness enhancement film. Also, thefluorescent sheet may be a transparent plate or film including afluorescent material.

The reflective sheet 1130 may be disposed under the light guide member1120, and may serve to reflect light emitted from the bottom surface ofthe light guide member 1120 toward a light emitting surface of the lightguide member 1120. The reflective sheet 1130 may be formed, for example,of a resin material having good reflectivity such as PET, PC, or PVCresins or other materials.

FIG. 20 shows a lighting unit 1200 that includes any one or more of theaforementioned embodiments of the light emitting device or lightemitting device package. This lighting unit includes a case body 1210, alight emitting module 1230 installed in the case body 1210, and aconnection terminal 1220 installed in the case body 1210 to be suppliedwith an electric power from an external power source.

The case body 1210 may be formed of a material having good heatshielding characteristic, for example, a metal material or a resinmaterial.

The light emitting module 1230 may include a substrate 700, and at leastone light emitting device package 600 mounted on the substrate 700. Inthe light emitting module 1230 according to the current embodiment, itis illustratively shown that the light emitting device packages 600 aremounted on the substrate 700, but the light emitting devices accordingto any of the embodiments described herein may be mounted directly onthe substrate 700.

The substrate 700 may be an insulator substrate on which a circuitpattern is printed and may include, for example, a general printedcircuit board (PCB), a metal core PCB, a flexible PCB, a ceramic PCB,etc. Also, the substrate 700 may be formed of a material to efficientlyreflect light, and a surface thereof may be formed in a color capable ofefficiently reflecting light, for example, white color, silver color, orthe like.

At least one light emitting device package may be mounted on thesubstrate 700. Each of the light emitting device packages 200 mayinclude at least one light emitting diode (LED). The light emittingdiode may include a color LED emitting red, green, blue or white light,and a UV LED emitting ultraviolet (UV).

The light emitting module 1230 may have a combination of several LEDs soas to obtain desired color and luminance. For example, the lightemitting module 1230 may have a combination of a white LED, a red LED,and a green LED so as to obtain a high color rendering index (CRI). Afluorescent sheet may be further disposed on a path of light emittedfrom the light emitting module 1230. The fluorescent sheet converts thewavelength of the light emitted from the light emitting module.

For example, when the light emitted from the light emitting module 1230has a blue wavelength band, the fluorescent sheet may include a yellowfluorescent material, so that the light, which is emitted from the lightemitting module 1230 and passes through the fluorescent sheet, finallyappears as white light.

The connection terminal 1220 may be electrically coupled to the lightemitting module 1230 to supply an electric power to the light emittingmodule 1230. As shown in FIG. 19, the connection terminal 1220 may bescrewed and coupled to an external power, but the invention is notlimited thereto. For example, the connection terminal 1220 may be madein a pin type and inserted into an external power, or may be connectedto the external power through a power line.

As described above, the lighting system may include at least one of alight guide member, a diffusion sheet, a light-condensing sheet, abrightness enhancement sheet and a fluorescent sheet on a traveling pathof light to obtain a desired optical effect. Because the lighting systemincludes a light emitting device or package having superior lightefficiency, the lighting system can show superior light efficiency aswell.

One or more embodiments described herein, thus, provide a light emittingdevice having a novel structure and a method of manufacturing the same.One or more of these embodiments also provide a light emitting devicewith enhanced light efficiency, and a method of manufacturing the same.One or more of these embodiments, also provide a light emitting deviceand a method of manufacturing the same in which a growth substrate canbe easily separated.

In one embodiment, a light emitting device comprises: a firstsemiconductor layer; a second semiconductor layer; and an active layerbetween the first and second semiconductor layers, the firstsemiconductor layer includes a first surface facing the active layer,and a second surface oppositely facing the first surface, and the firstsemiconductor layer has a stepped portion formed at a side surfacethereof and thus the area of the second surface is smaller than amaximum area of the first semiconductor layer.

In another embodiment, a light emitting device package comprises: apackage body; a first conductivity layer and a second conductivity layeron the package body; a light emitting device disposed on the packagebody and electrically connected to the first conductivity layer and thesecond conductivity layer; and a molding member enclosing the lightemitting device, wherein the light emitting device includes a firstsemiconductor layer, a second semiconductor layer, and an active layerbetween the first semiconductor layer and the second semiconductorlayer, the first semiconductor layer includes a first surface facing theactive layer, and a second surface oppositely facing the first surface,and the first semiconductor layer has a stepped portion formed at a sidesurface thereof and thus the area of the second surface is smaller thana maximum area of the first semiconductor layer.

In a further embodiment, a lighting system comprises: a light emittingmodule including a substrate; and a light emitting device on thesubstrate, wherein the light emitting device comprises: a firstsemiconductor layer; a second semiconductor layer; and an active layerbetween the first semiconductor layer and the second semiconductorlayer, the first semiconductor layer includes a first surface facing theactive layer, and a second surface oppositely facing the first surface,and the first semiconductor layer has a stepped portion formed at a sidesurface thereof and thus the area of the second surface is smaller thana maximum area of the first semiconductor layer.

In still another embodiment, a method of manufacturing a light emittingdevice, comprises: forming a mask layer defining a plurality of lightemitting structure layer growth regions on a growth substrate; forming alight emitting structure layer including a first conductivity typesemiconductor layer, an active layer and a second conductivity typesemiconductor layer from the light emitting structure layer growthregions; selectively removing the light emitting structure layer andforming a first electrode on the first conductivity type semiconductorlayer and a second electrode on the second conductivity typesemiconductor layer; and cutting the growth substrate and the mask layerto separate the growth substrate and the light emitting structure layer.

In yet another embodiment, a method of manufacturing a light emittingdevice, comprises: forming a mask layer defining a plurality of lightemitting structure layer growth regions on a growth substrate; forming alight emitting structure layer including a first conductivity typesemiconductor layer, an active layer and a second conductivity typesemiconductor layer from the light emitting structure layer growthregions; forming a protective layer between the light emitting structurelayers; forming a second electrode on the light emitting structure layerand the protective layer; separating the growth substrate and removingthe mask layer and the protective layer; forming a first electrode onthe first conductivity type semiconductor layer; and cutting the secondelectrode to separate the second electrode and the light emittingstructure layer.

In accordance with another embodiment, a light emitting device comprisesa first semiconductor layer; a second semiconductor layer; and an activelayer between the first and second semiconductor layers, wherein thefirst semiconductor layer includes a first surface facing the activelayer, a second surface opposing the first surface, and a side surfacethat includes a stepped portion. The stepped portion causes the sidesurface to extend beyond one of the first surface or second surface.

The area of the first surface may be greater than an area of the secondsurface, the area of the second surface may be less than the area of thefirst surface as a result of the stepped portion, or an area of thefirst surface may be less than an area of the second surface. Inaddition, the first semiconductor layer is a first conductivity type andthe second semiconductor layer is a second conductivity type.

The device may also include a buffer layer, wherein a firstsemiconductor layer is located between the buffer layer and activelayer, the first semiconductor layer is of a first conductivity type,and the second semiconductor layer is of a second conductivity type. Thebuffer layer may be on a first portion of the first conductivity typesemiconductor, and the device may further comprise a first electrode onthe first semiconductor layer where the buffer layer is not formed and asecond electrode under the second semiconductor layer.

The buffer layer may be divided into first and second sections disposedon the first semiconductor layer, the first and second sections of thebuffer layer separated to expose a portion of the first semiconductorlayer, the first electrode electrically coupled to the exposed portionof the first semiconductor layer. The buffer layer may be an undopedlayer or a doped layer, and if undoped may include a nitride.

The device may further include at least one reflector to reflect lightemitted from the active layer. The reflector is located adjacent thefirst semiconductor layer, and may be formed as a protrusion thatextends from a surface of a substrate that supports or is coupled to thefirst semiconductor layer.

The device may also include at least one diffuser, located on the secondsurface of the first semiconductor layer, to diffuse light emitted fromthe active layer. The diffuser may extend into the second surface of thefirst semiconductor layer, and may include a recess that extends intothe second surface of the first semiconductor layer.

In accordance with another embodiment, a light emitting device comprisesa buffer layer, a first semiconductor layer, a second semiconductorlayer, and an active layer between the first and second semiconductorlayers. The first semiconductor layer is between the buffer layer andactive layer, the active layer is between the first and secondsemiconductor layers, and a bottom surface of the buffer layer has anarea smaller than an area of at least one of the surfaces of the firstsemiconductor layer.

Additionally, a side surface of the buffer layer may includes a steppedportion which causes a top surface of the buffer layer facing the firstsemiconductor layer to have an area greater than the bottom surface ofthe buffer layer.

Additionally, a side surface of the buffer layer may includes a steppedportion which causes the side surface of the buffer layer to extendbeyond at least one of a top surface or the bottom surface of the bufferlayer. The buffer layer may be a doped layer or an undoped layer.

In addition, the device may include at least one reflector to reflectlight emitted from the active layer. The reflector may be adjacent thebuffer layer and may include a protrusion that extends from a surface ofa substrate that supports or is coupled to the buffer layer.

A light emitting device package may be formed to comprise a lightemitting device in accordance with any one of the aforementionedembodiments.

In accordance with another embodiment, a lighting system comprises alight emitting device as recited in claim 1, wherein said device iscoupled to a substrate of a light emitting module.

In accordance with another embodiment, a method of manufacturing a lightemitting device comprises forming a mask layer on a substrate to definea region of a light emitting device; forming a semiconductor layer of afirst conductivity type, an active layer, and a semiconductor layer of asecond conductivity type at said region; selectively removing the masklayer; and forming first and second electrodes electrically coupled tothe first and second semiconductor layers respectively, wherein one ofthe semiconductor layers is formed to include a first surface facing theactive layer, a second surface opposing the first surface, and a sidesurface that includes a stepped portion, and wherein the stepped portioncauses the side surface to extend beyond one of the first surface orsecond surface.

In accordance with another embodiment, a method of manufacturing a lightemitting device, comprises forming a mask layer on a substrate to definea region of a light emitting device; forming a semiconductor layer of afirst conductivity type, an active layer, and a semiconductor layer of asecond conductivity type at said region; selectively removing the masklayer; and forming first and second electrodes electrically coupled tothe first and second semiconductor layers respectively, wherein one ofthe semiconductor layers is formed to include a first surface facing theactive layer.

The method further includes forming a buffer layer coupled to the firstand second semiconductor layers and the active layer, wherein a bottomsurface of the buffer layer has an area smaller than an area of at leastone of the surfaces of the semiconductor layer of the first conductivitytype or the second conductivity type. Also, buffer layer may include astepped portion that causes the bottom surface of the buffer layer tohave an area smaller than an area of at least one of the surfaces of thesemiconductor layer of the first conductivity type or the secondconductivity type.

Herein, when a layer (or film) is referred to as being “on” anotherlayer or substrate, it understood that it can be directly on the otherlayer or substrate, or that intervening layers may be present betweenthem. Further, it will be understood that when a layer is referred to asbeing “under” another layer, it can be directly under the other layer,and or that one or more intervening layers may be present. In addition,it is to be understood that when a layer is referred to as being“between” two layers, that layer may be the only one between the twolayers or one or more intervening layers may also be present betweenthem.

In the figures, the dimensions of layers and regions are exaggerated forclarity of illustration. In addition, the dimension of each part doesnot reflect an actual size.

Any reference in this specification to “one embodiment,” “anembodiment,” “example embodiment,” etc., means that a particularfeature, structure, or characteristic described in connection with theembodiment is included in at least one embodiment of the invention. Theappearances of such phrases in various places in the specification arenot necessarily all referring to the same embodiment. Further, when aparticular feature, structure, or characteristic is described inconnection with any embodiment, it is submitted that it is within thepurview of one skilled in the art to effect such feature, structure, orcharacteristic in connection with other ones of the embodiments.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

1. A light emitting device comprising: a first semiconductor layer; asecond semiconductor layer; and an active layer between the first andsecond semiconductor layers, wherein the first semiconductor layerincludes: (a) a first surface facing the active layer, (b) a secondsurface opposing the first surface, and (c) a side surface that includesa stepped portion, wherein the stepped portion causes the side surfaceto extend beyond one of the first surface or second surface.
 2. Thedevice of claim 1, wherein an area of the first surface is greater thanan area of the second surface.
 3. The device of claim 2, wherein thearea of the second surface is less than the area of the first surface asa result of the stepped portion.
 4. The device of claim 1, wherein anarea of the first surface is less than an area of the second surface. 5.The device of claim 1, wherein the first semiconductor layer is a firstconductivity type and the second semiconductor layer is a secondconductivity type.
 6. The device of claim 1, further comprising: abuffer layer, wherein a first semiconductor layer is located between thebuffer layer and the active layer, the first semiconductor layer is of afirst conductivity type, and the second semiconductor layer is of asecond conductivity type.
 7. The device of claim 6, wherein the bufferlayer is formed on a first portion of the first conductivity typesemiconductor, and wherein the device further comprises: a firstelectrode on the first semiconductor layer where the buffer layer is notformed, and a second electrode under the second semiconductor layer. 8.The device of claim 7, wherein the buffer layer is divided into firstand second sections disposed on the first semiconductor layer, the firstand second sections of the buffer layer separated to expose a portion ofthe first semiconductor layer, the first electrode electrically coupledto the exposed portion of the first semiconductor layer.
 9. The deviceof claim 6, wherein the buffer layer is an undoped layer.
 10. The deviceof claim 6, wherein the buffer layer is a doped layer.
 11. The device ofclaim 1, further comprising: at least one reflector to reflect lightemitted from the active layer.
 12. The device of claim 11, wherein thereflector is located adjacent the first semiconductor layer.
 13. Thedevice of claim 12, wherein the reflector includes: a protrusion thatextends from a surface of a substrate that supports or is coupled to thefirst semiconductor layer.
 14. The device of claim 1, furthercomprising: at least one diffuser, located on the second surface of thefirst semiconductor layer, to diffuse light emitted from the activelayer.
 15. The device of claim 14, wherein the diffuser extends into thesecond surface of the first semiconductor layer.
 16. The device of claim15, wherein the diffuser includes a recess that extends into the secondsurface of the first semiconductor layer.
 17. A light emitting devicecomprising: a buffer layer; a first semiconductor layer; a secondsemiconductor layer; and an active layer between the first and secondsemiconductor layers, wherein: the first semiconductor layer is betweenthe buffer layer and active layer, the active layer is between the firstand second semiconductor layers, and wherein a bottom surface of thebuffer layer has an area smaller than an area of at least one of thesurfaces of the first semiconductor layer.
 18. The device of claim 17,wherein a side surface of the buffer layer includes: a stepped portionwhich causes a top surface of the buffer layer facing the firstsemiconductor layer to have an area greater than the bottom surface ofthe buffer layer.
 19. The device of claim 17, wherein a side surface ofthe buffer layer includes: a stepped portion which causes the sidesurface of the buffer layer to extend beyond at least one of a topsurface or the bottom surface of the buffer layer.
 20. The device ofclaim 17, wherein the buffer layer is a doped layer.
 21. The device ofclaim 17, wherein the buffer layer is an undoped layer.
 22. The deviceof claim 17, further comprising: at least one reflector to reflect lightemitted from the active layer.
 23. The device of claim 22, wherein thereflector is adjacent the buffer layer.
 24. The device of claim 23,wherein the reflector includes: a protrusion that extends from a surfaceof a substrate that supports or is coupled to the buffer layer.
 25. Alight emitting device package comprising the light emitting device ofclaim
 1. 26. A light emitting device package comprising the lightemitting device of claim
 17. 27. A lighting system comprising a lightemitting device as recited in claim 1, wherein said device is coupled toa substrate of a light emitting module.
 28. A method of manufacturing alight emitting device, comprising: forming a mask layer on a substrateto define a region of a light emitting device; forming a semiconductorlayer of a first conductivity type, an active layer, and a semiconductorlayer of a second conductivity type at said region; selectively removingthe mask layer; and forming first and second electrodes electricallycoupled to the first and second semiconductor layers respectively,wherein one of the semiconductor layers is formed to include a firstsurface facing the active layer, a second surface opposing the firstsurface, and a side surface that includes a stepped portion, and whereinthe stepped portion causes the side surface to extend beyond one of thefirst surface or second surface.
 29. A method of manufacturing a lightemitting device, comprising: forming a mask layer on a substrate todefine a region of a light emitting device; forming a semiconductorlayer of a first conductivity type, an active layer, and a semiconductorlayer of a second conductivity type at said region; selectively removingthe mask layer; and forming first and second electrodes electricallycoupled to the first and second semiconductor layers respectively,wherein one of the semiconductor layers is formed to include a firstsurface facing the active layer, said method further comprising: forminga buffer layer coupled to the first and second semiconductor layers andthe active layer, wherein a bottom surface of the buffer layer has anarea smaller than an area of at least one of the surfaces of thesemiconductor layer of the first conductivity type or the secondconductivity type.
 30. The method of claim 29, wherein the buffer layerincludes a stepped portion that causes the bottom surface of the bufferlayer to have an area smaller than an area of at least one of thesurfaces of the semiconductor layer of the first conductivity type orthe second conductivity type.